What is the Ishikawa Fishbone? : What is the Ishikawa Fishbone? The cause & effect diagram or Ishikawa Fishbone is the brainchild of Kaoru Ishikawa, who pioneered quality management processes in the Kawasaki shipyards, and in the process became one of the founding fathers of modern management.
What is it used for? : What is it used for? The cause and effect diagram is used to explore all the potential or real causes (or inputs) that result in a single effect (or output).
Causes are arranged according to their level of importance or detail, resulting in a depiction of relationships and hierarchy of events.
This can help you search for root causes, identify areas where there may be problems, and compare the relative importance of different causes.
Slide 5: Follow these steps to solve a problem with Ishikawa Fish Bone:
Stage 1: Identify the problem:Write down the exact problem you face in detail. Where appropriate identify who is involved, what the problem is, and when and where it occurs. Write the problem in a box on the left hand side of a large sheet of paper. Draw a line across the paper horizontally from the box. This arrangement, looking like the head and spine of a fish, gives you space to develop ideas.
Stage 2: Work out the major factors involved:Next identify the factors that may contribute to the problem. Draw lines off the spine for each factor, and label it. These may be people involved with the problem, systems, equipment, materials, external forces, etc. Try to draw out as many possible factors as possible. If you are trying to solve the problem as part of a group, then this may be a good time for some brainstorming.
Stage 3: Identify possible causes:For each of the factors you considered in stage 2, brainstorm possible causes of the problem that may be related to the factor. Show these as smaller lines coming off the 'bones' of the fish. Where a cause is large or complex, then it may be best to break the it down into sub-causes. Show these as lines coming off each cause line.
Stage 4: Analyze your diagram:By this stage you should have a diagram showing all the possible causes of your problem that you can think of. Depending on the complexity and importance of the problem, you can now investigate the most likely causes further. This may involve setting up investigations, carrying out surveys, etc. These will be designed to test whether your assessments are correct.
Thinks to keep in mind!! : Thinks to keep in mind!! Take care to identify causes rather than symptoms. Post diagrams to stimulate thinking and get input from other staff.
Self-adhesive notes can be used to construct Ishikawa diagrams. Sources of variation can be rearranged to reflect appropriate categories with minimal rework.
Insure that the ideas placed on the Ishikawa diagram are process variables, not special caused, other problems, tampering, etc.
Review the quick fixes and rephrase them, if possible, so that they are process variables.